Starting switch for single-phase motors



R. C. -LEAKE Aug. 11, 3925. L549,009

L1: w m 5 a ATTORNEY.

STARTING SWITCH FOR SINGLE PHASE MOTORS Filed June 7-, 1920 3 Sheets-Sheet 1 man;

IIIII 1 TZR.

Aug. 11, E925.

1,549,009 R. c. LEAKE STARTING SWITCH FOR SINGLE PHASE MOTORS Filed June 7, 1920 s Sheets-Sheet 2 L) w w m r r Aug. 11, 1925.

R. C. LEAKE STARTING SWITCH FOR SINGLE PHASE MOTORS Filed June 7, 1920 3 Sheets-Sheet s mm WTTORA'EK Patented Aug. 11, 1 925. 1

UNITED STATES PATENT OFFICE.

RICHARD C. LEAKE, OF ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL RAILWAY SIGNAL COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

STARTING SWITCH FOR SINGLE-IPHASE MOTORS.

Application filed June 7, 1920. Serial No. 387,127.

To altwhom it may concern:

Be it known that I, RICHARD C. Luann, citizen of the United States, residing at Rochester, in the county of Monroe and to devise a speed-responsive switch which will act positively to break and make the desired circuit connections at predetermined speeds, which will break-contact quickly and spread the are over a comparatively large surface, thereby avoiding injury of the con tacts, and which will possess the various other features of construction and operation desirable in switches of this type. My improved switch is also arranged and constructed so as to act as a fan and. blow air through the motor for ventilating and cooling it, thereby avoiding the expense and complication of an extra fan for this purose.

Other specifid features and advantages will appear hereinafter as the description progresses.

In describing the invention in detail reference will be made to the accompanying drawings in which:-

Figure 1 is a diametrical section through a conventional sin le phase motor showing my improved starting switch applied there- Fig. 2 is a transverse section through the motor and switch on the line 2-2 in Fig. 1;

Fig. 3 is a fragmentary inside view of the end cap of the motor and shows the arrangement of contact posts;

Fig. 4 is a view similar to Fig. 3 showing a modified construction of the stationary contact blocks;

- Fig. 5 is a diametrical section on a line 5-5 in Fig.4; and n Fig. 6 shows the switch diagrammatically in perspective, with parts brokenaway and spread apart, together with the circultconnections preferably employed with the switch.

Referring to the accompanying drawings, I have shown my improved centrifugal havin switch applied to a single phase motor of conventional construction comprising a frame F, a laminated stator S with coils or windings N constituting the usual starting and running windings for the stator, and a rotor R fixed to a shaft 1, which is journaled in bushings 2 pressed in bearing housings 3 integral with the end caps C of the motor. These end caps C are provided with ventilating openings 4 (see Fig. 3) which are covered by a splash cover or shield D. In the shield D is a hole lined with an insulating bushing 5 for receiving the power wires. The end cap C and shield D are fastened to the frame F by nuts 6 on threaded rods 7 extending through th motor.

Secured to the end caps C are three insulated contact posts 8, 8 8, (see Figs. 1 and'3) which are arranged at substantially equal intervals around the shaft 1. Each of these contact posts comprises a block 9, preferably made of German silver or similar material, and a stem 10 which has a flared head countersunk in said block and which is fastened 'tothe end cap C but insulated therefrom. The stem 10 extends through a bushing 11 and washers 12 of insulated material, and is provided with a nut 13 for clamping the stem to the end cap C. Two of the posts 8 and 8 have additional nuts for attaching wires. An extra bindin post 15, supported and insulated in a similar manner, but having no contact block is also secured to the end cap C to provide attachment for other wires leading to the stator winding, these wires being taken through an insulated bushing in the end cap O.

Cooperating with the three contact posts 8 to 8 is a contact ring 16, preferably made of phosphor bronze, steel or a similar comparatively hard conducting material. This ring 16 is fastened by tubular rivets 17 to a disk 18 of insulating material fitting loosely on the shaft 1, each of these rivets also passing through a spacer 19 and a ring 20, both of insulating material. A sleeve 21 on the shaft 1 is provided with a flange 21" having a loose slip fit with the circular groove formed between the disk 18 and the ring 20. Fastened to the sleeve 21 is a circular member 22 radially extending arms' 23 with curve ends. In the construction illustrated there are three of these arms 23 arranged 120 apart around the shaft 1, as shown in Fig. 2. Fastened to the rotor R-by screws 24, is a plate 25 which is formed with three pairs of cars or projections 26 arranged 120 apart and straddling the arms 23. These projections 26 are shaped as shown in Fig. 1 and constitute in efl'ect fan blades.

Associated with each pair of the projections 26 is one of the centrifugal elements of the switch. This element comprises a weight in the form of a roller'27 loosely journaled on a pin 28 carried by the lower ends of a pair of links 29, which are pivotally supported at their'upper ends on a pin 30 fastened to the projections 26. A collar 31 is fastened to the plate 25 and constitutes a guilding sup rt for the inner end of the sleeve 21. irother collar 32, having a sliding fit on the shaft 1, guides the outer end of the sleeve 21; and between these collars 31 and 32 is a compression spring 33 surrounding said shaft.

Operatiom-When the rotor and shaft 1 are at rest, the parts are in the position shown, the rollers 27 being in their inner position, and the contact ring 16 being pressed by the spring 33 against the blocks 9 of the contact posts 88. These contact posts form a threepoint support for the contact ring 16, thereby assuring intimate contact with each block 9. When the centrifugal force into contact with the arms 23, and at a predetermined speed, the pressure exerted by these rollers against these arms overcomes the tension of the spring 33 and slides the sleeve 21 axially on the shaft 1, the outer movement of said rollers being limited by the curved ends of the arms 23. As the sleeve 21 is shifted, the contact ring 16 is pulled away from the contact blocks 9, thereby breaking the circuit through the starting windin As soon as the contact ring 16 leaves t e blocks 9, it accelerates, and all of the parts revolve together with the shaft 1, without any engagement or rubbin between stationary and moving parts. f the speed of the motor falls below ai-critical speed, the sprin 33 overcomes the centrifugal force exerte by the rollers 27 and returns the parts to the position shown, thereby again cutting in the starting winding. The projections 26 act as fan blades and drawthe air in through the usual ventilating holes in the rotor and propel it by the ventilating openings 4 in the end cap 0. This constitutes one of the important features of the invention since it obviates the expense and complication of a special ventilating fan.

Referring to Fig. 6, 35 designates the running winding, and 36 the starting winding. When the switch 37 is closed, the running winding 35 is connected directly across the supply conductors 38, and the starting wind ing 36 is connected in multiple therewith between the contact posts 8 and 8 The contact post 8 is a dead post which. is used with the other two so as to bear against the contact plate 16 at three points.

()ne important feature of my invention, is the uick action of the switch. It will be noted at when the rollers 27 move the arms 23, the angle of the links 29 changes, and this increases the component of the centrifugal force parallel with the shaft 1 and acting on the arms 23, and also that the radius of rotation of the rollers 27 also increases at the same time. As a result, when the rollers 27 overcome the tension of the spring 33 and start their outward movement, they fly out quickly, because they have an increased mechanical advantage over the spring 33 as they move out, and also acquire an increased speed and consequently an increased centrifugal force. ThlS quick movementof the contact ring 16, similar to the operation of a snap switch, prevents burning or injury of the contacts by long drawn out arcs. Also, as soon as the pressure of the contact ring 16 on the blocks 9 is relaxed, this ringcommences torotate so that any are that may be drawn is spread over a comparatively wide surface, thereby obviating local heating and pitting. It is found in practice that minute projections are sometimes drawn up on the contacts by the arcing, but these projections are rubbed down when the motor slows down and stops, so that the contact ring and blocks maintain a serviceable surface after a large number of Operations. 7

While considerable wear of the contacts may take place, both on the ring 16 and the blocks 9, without materially altering the critical speed at which the switch will open, suchwear may be reduced, if desired, by increasing the area of the stationary contacts 9. Such an arran ement is shown in Figs. 4 and 5, in whicii two segmental contact blocks 40 and 40 are secured to the end 'In this modified construction the shape of the ventilating openings 4 is changed.

The specific constructions shown and dcscribedare merely illustrative of the'inven- 15c:

tion and are susceptible of adaptation and modification in practice without departing from the invention.

What I claim as new and desire to secure by Letters Patent of the United States is 1. In a centrifugal switch, the combination with a shaft, of a sleeve movable axially on the shaft and biased in one direction, centrifugal members carried by pivoted levers connected to the shaft and acting to move the sleeve inthe other direction, said mem bers in moving outward increasing the component of their centrifugal force acting on the sleeve, and circuit controlling means actuated by said sleeve.

2. In a centrifugal switch, the combination with a shaft, of a sleeve movable axially on the shaft and havingradial arms, a member rotating with the shaft and having pairs of projections straddling the said arms, centrifugal members pivotally supported by links from said projections and arranged tobear against the corresponding arms, a spring biasing the sleeve inone direction, and circuit controlling means actuated by the sleeve.

3. A centrifugal switch for starting single phase induction motors comprising a plurality of insulated contact postssecured to an end plate of the motor, an insulated contact ring movable axially on the motor shaft, a spring acting to press said ring against the contact posts, and speed-responsive means comprising a roller carried by a lever for moving the ring in opposition to said spring, and a support for said lever attached to the end of the rotor and having a plurality of radially extending flat projections adapted to act as fan blades.

4. A centrifugal switch' comprising, in combination with a shaft, a contact ring movable axially on the shaft, insulated stationary contacts cooperating with said ring, pivoted rollers carried by movable levers for actuating said ring into engagement with said stationary contacts, and supports for said levers formed with radial projections acting as, fan blades.

5. In a centrifugal switch, the combination with a shaft, of a sleeve movable axially on the shaft and biased in one direction, a centrifugal device including members carried by the shaft and acting to move the sleeve in the other direction, said members in moving outward increasing the compo nent of the force produced by said centrifugal device upon the sleeve, and circuit controlling means actuated by said sleeve.

6. In a centrifugal switch, the combination with a shaft, of a sleeve movable axially on the shaft and biasedin one direction, a centrifugal device comprising swingingly supported heavy rollers acting to move the sleeve in the other direction, said rollers in moving outward transmitting an increasing compo-nent of their centrifugal force upon the sleeve, and circuit controlling means actuated by said sleeve.

In testimony whereof I have afiixed my signature. 5

RICHARD o. 'LEAKE. 

